Feature/fix build without modules

[ClausKlein]

cmake export config package

after install release and debug:

bash-5.3$ tree stagedir/lib/
stagedir/lib/
├── cmake
│   └── beman.execution
│       ├── beman.execution-config-version.cmake
│       ├── beman.execution-config.cmake
│       ├── beman.execution-targets-debug.cmake
│       ├── beman.execution-targets-relwithdebinfo.cmake
│       ├── beman.execution-targets.cmake
│       ├── bmi-GNU_Debug
│       │   └── beman.execution.gcm
│       ├── bmi-GNU_RelWithDebInfo
│       │   └── beman.execution.gcm
│       ├── cxx-modules
│       │   ├── cxx-modules-beman.execution-Debug.cmake
│       │   ├── cxx-modules-beman.execution-RelWithDebInfo.cmake
│       │   ├── cxx-modules-beman.execution.cmake
│       │   ├── target-execution-Debug.cmake
│       │   └── target-execution-RelWithDebInfo.cmake
│       └── modules
│           └── execution.cppm
├── libbeman.execution.a
└── libbeman.execution_d.a

7 directories, 15 files
bash-5.3$ 

1606eaa Add support for CMAKE_SKIP_INSTALL_RULES
c5cb050 Fix installation without cxx_modules
3bb4ba9 Use beman-install-library-config.cmake (local patched version!)
fd9ae94 Feat: configure project to test without modules

• Needs final cleanup

[ClausKlein]

@ednolan @nickelpro see too https://discourse.cmake.org/t/how-to-install-multiple-file-set-for-a-library-in-a-generic-way/15489/4